As I understand the buttons,
"a" directs all air up, full fan, full heat. Power Defrost.
"b" directs air
up and down, with center vents if cooling, A/C compressor enabled.
"c" directs air down, 'leak' air up, center vents if cooling, A/C compressor enabled.
"d" directs air down, 'leak' air up, with center vents if cooling, A/C compressor disabled.
"e" is OFF.
55F weather is hard to defrost, you want 'dry' air coming from the vents. Air is 'dried' when it is cooled below dew point, and then reheated.
I'll suggest using "b" and selecting a heating temperature that will result in reheated, warmer, drier air from the windshield vents. If you select a colder temperature, the glass will be cooled and more water will condense, making the problem worse.
Try using Defrost to get the glass clear, and then "b" to keep it clear, with perhaps an occasional manual Fast fan speed to stir up the air?
Hope this works, let us know.
Best Regards,
Jim